[llvm] [LegalizeTypes][RISCV] Use SPLAT_VECTOR_PARTS to legalize splat BUILD_VECTOR (PR #107290)

[Philip Reames via llvm-commits]

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@@ -14,9 +14,11 @@ define <1 x i64> @llrint_v1i64_v1f32(<1 x float> %x) {
 ; RV32-NEXT:    vsetivli zero, 1, e32, m1, ta, ma
 ; RV32-NEXT:    vfmv.f.s fa0, v8
 ; RV32-NEXT:    call llrintf
-; RV32-NEXT:    vsetivli zero, 2, e32, mf2, ta, ma
-; RV32-NEXT:    vmv.v.x v8, a0
-; RV32-NEXT:    vslide1down.vx v8, v8, a1
+; RV32-NEXT:    sw a1, 4(sp)
+; RV32-NEXT:    sw a0, 0(sp)
+; RV32-NEXT:    mv a0, sp
+; RV32-NEXT:    vsetivli zero, 1, e64, m1, ta, ma
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preames wrote:

Given the results on short VL, we'd probably be better going through the buildvector lowering, or adapting some of that lowering to work on short splat_vector_parts.  Using the strided load may not always be our best fallback.  

(Optional follow up only)

https://github.com/llvm/llvm-project/pull/107290